Grease 9-inch springform pan.
Line bottom with waxed paper; grease waxed paper.
In small bowl, pour rum over graham crackers.
When crackers are softened, mash with fork.
In large bowl, beat egg yolks with electric mixer at medium speed until lemon colored.
Add sugar and orange peel; beat at high speed until thickened, about 3 minutes.
Beat cracker mixture into yolk mixture.
In large mixer bowl using clean beaters, beat egg whites and cream of tartar at high speed until stiff, but not dry, peaks form.
Gently fold beaten whites, ground walnuts and grated chocolate into yolk mixture.
Pour batter into prepared pan.
Bake in preheated 350°F oven 45 to 50 minutes or until toothpick inserted in center comes out clean and small crack appears on surface.
Let cool completely in pan on wire rack.
Remove side of springform pan.
Invert cake onto serving plate; remove bottom of pan and waxed paper.
Place strips of waxed paper under edge of cake to cover plate.
In top of double boiler, melt chocolate squares and butter over simmering water, stirring to blend.
Stir in honey.
Pour chocolate mixture over cake; let stand until slightly cool.
Spread over top and side of cake.
Remove waxed paper strips.
Garnish with walnut halves.
When firm, cut into thin wedges.